1. Field of the Invention
This invention relates to an information storage medium and more particularly relates to methods, systems and apparatus for depositing magnetic material on patterned media to increase information storage density.
2. Description of the Related Art
Nearly every computer in use today uses one or more hard disk drives to store changing digital information in a relatively permanent form. Hard disk drives are also becoming increasingly pervasive in media players, digital recorders, and other personal devices.
Hard disks typically comprise high precision aluminum or glass disks coated on both sides with a special thin film media designed to store information in the form of magnetic patterns. The disks are rotated at high speeds, and electromagnetic read/write heads are used to either record information onto the thin film media, or read information from it.
Thin film media employed in hard disk drives have typically comprised a thin, continuous layer of magnetic grains that may be magnetized in a particular orientation by a strong magnetic field. A read/write head, for example, can record information by creating a 6local magnetic field that orients a cluster of grains, known as a bit, in one direction or the other. To increase the capacity of disk drives, manufacturers are continually striving to reduce the size of bits and the grains that comprise the bits.
The ability of individual magnetic grains to be magnetized in one direction or the other, however, poses problems where grains are extremely small. The superparamagnetic effect results when the product of a grain's volume (V) and its anisotropy energy (ku) fall below a certain value such that the magnetization of that grain may flip spontaneously. Where this occurs, data stored on the disk is corrupted. Thus, while it is desirable to make smaller grains to support higher density recording with less noise, grain miniaturization is inherently limited by the superparamagnetic effect.
In response to this problem, engineers have developed patterned media. In patterned media, the magnetic thin film layer is typically created as an ordered array of highly uniform islands, each island capable of storing an individual bit. Each bit may be one grain, or several exchange coupled grains, rather than a collection of random decoupled grains. In this manner, patterned media effectively reduces noise by imposing linear magnetic transitions.
Indeed, patterned media provides physical as well as magnetic separation of data, effectively circumventing the density limitations imposed by the superparamagnetic effect. Despite the advantages of such media, however, known patterned magnetic storage media are also inherently limited in data storage capacity by dimensional island requirements.
Known methods for producing patterned magnetic storage media deposit a blanket of magnetic material over the disk. This material collects on top of the islands, as well as in the valleys between the islands. If the islands are raised high enough above the valleys, the magnetic material on the tops of the islands is physically and magnetically isolated from adjacent islands, as well as from material in the valleys. Known methods for producing magnetic media thus inherently limit track density to match dimensional island requirements as such methods necessarily create just one recordable region per island.
From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method that increases track density while maintaining physical and magnetic separation of data. Beneficially, such an apparatus, system, and method would increase the effective area sensitive to read/write heads, increase data storage capabilities, decrease the flying distance of read/write heads, and optimize overall data storage performance. Such methods, systems and apparatus are disclosed and claimed herein.